[Object] To provide a polymeric material composition having high heat resistance, excellent compatibility, and greatly improved weatherability.
[Solving Means] A polymeric material composition containing:
a polymeric material and a triazine compound having the general formula (I):

wherein R 1 to R 3 denote an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an alkylaryl group, or an arylalkyl group, these groups being optionally substituted by a hydroxy group, a halogen atom, a cyano group, a nitro group, an alkyl group, or an alkoxy group, and/or being optionally interrupted by an oxygen atom, a sulfur atom, a carbonyl group, an ester group, an amide group, or an imino group; R 4 to R 6 denote an alkyl group or an alkenyl group; and R 7 to R 9 denote a hydrogen atom, a halogen atom, an alkyl group, or an alkenyl group.